"Modern envy" is rampant, thanks to Facebook, Instagram, and other social media platforms, says Jennifer Breheny Wallace in a recent Wall Street Journal article. And although this seems to be a bad thing, it doesn't have to be, she explains.

"Researchers are finding that, if approached the right way, there can actually be an upside to this deadly sin," says Wallace.

Psychologists classify envy in two ways, she says: malicious, where you "want to cut the advantaged person down so you look better by comparison," and benign, where you are "motivated by another person's success and strive to emulate it."

In 2011, researchers in the Netherlands conducted a series of experiments with more than 200 university students and found that when they triggered feelings of benign envy in the students, it drove them to study more and perform better on a test.

In a separate experiment, researcher Sarah E. Hill and others found that envy can improve attention and memory — "the tools needed to copy a rival's steps to success," Wallace says. "Not only can envy motivate us to reach for higher goals, it may even give us the cognitive push to get there."

Envy can work in your favor at the office, too.

In a 2010 Harvard Business Review paper, business school professors Tanya Menon and Leigh Thompson evaluated envy among hundreds of executives and their organizations for a decade. "While the case studies showed that unchecked envy can damage careers and organizations, the authors also found that envy can be put to good use," Wallace says. "Your 'envy reflex,' they write, can point you in the right direction, focusing your time and attention on the areas that are important to you."

So if you find yourself envying someone else's success, consider it a powerful signal that you'd like some of what they have. Then go out and get it.